If you press A on the red mii plaza(or whatever title you need to reinstall) titlekey it should show you 3 options the first one is "Install from CDN"(click that) when it asks for version just press A and wait until is done. I think we can't share the .cia due to Nintendo copyrighted stuff
Thanks to this guy right here I fixed it. He has no idea how much he has done for me right now. I have severe OCD and I mean severe. I was ready to bash my head against the wall because this thing wasn't perfect. He mentioned CIA, I went and I got it from old3dsxl and it works on my new3ds. I had to create a custom badge with a shortcut to Mii Plaza and inject that into the 3ds, placed the badge and it launches. Thank you so freaking much.
And thank everyone else for trying to help.

